The assignee of the present invention manufactures and deploys spacecraft for, inter alia, communications and broadcast services. Market demands for such spacecraft have imposed increasingly stringent requirements for payload flexibility and utilization efficiency. For example, most communications satellites contain multiple receive and transmit beams, and often it is not possible to accurately forecast the demand for satellite capacity in each beam, especially in developing market areas. Over the lifetime of a satellite, which can be more than 10-15 years, it is typical for demand of satellite services to increase more in some coverage areas and less in other coverage areas. Forecasting the regions in which demand increases will occur and the magnitude of the increase (region-by-region) is extraordinarily difficult.
The most common design technique to provide on-orbit flexibility that addresses the uncertainty in space segment demand is to implement analog radio frequency (RF) switches in key locations in the payload. For example, mechanical RF switches are usually placed in the input multiplexing networks and at the outputs of some of the high power RF amplifiers in the spacecraft payload. The switches in the vicinity of the input multiplexer (IMUX) are commandable in-orbit and can be set to steer bandwidth to beams where demand is high (and away from lower demand beams), typically in bandwidth increments of 27, 36, 54, or 72 MHz.
The switches at the outputs of the power amplifiers are also commandable in-orbit and may be configured to direct RF power to beams where demand is strong (and away from beams where demand is weak). The RF power is generally directed in increments equal to the rated (or “saturated”) power of an individual amplifier, which may typically range from 10 to 200 W. Together, the switches in the IMUX and the switches after the amplifiers permit a satellite operator to tailor the bandwidth and RF power allocations among multiple coverage areas and beams to match the demand profile for satellite services. Such tailoring permits the operator to improve the overall usage and revenue generation of a communications satellite. However, because of spacecraft resource limitations of volume (for mounting hardware and routing cables and waveguides), mass, and thermal capacity, there is usually a limit to the number of amplifiers, output power of which may be routed to multiple beams.
Thus, there is a desire to find improved techniques that enable commandably reallocating RF bandwidth and RF power available for communications signals among a number of antenna beams to better match satellite resources to end user demand.